Privacy probably doesn't strictly monopolize HN's concerns because cloud services are Good Enough when it comes to privacy for our Ruby on Rails MVPs, our benign blogs, and our JSconf slideshows.
Conflating privacy where privacy is needed with privacy for privacy's sake is a waste of time and dilutes real privacy concerns with a bunch of "Wolf!" cries.
One example of a huge cloud-based privacy problem: Google Analytics, which I discovered by using NoScript.
So, google knows about me even when I don't use it. Even when I am explicitly avoiding it, and use DuckDuckGo instead (I do, by the way). Your "benign blog" which uses this service is hurting my privacy big time. I'm okay with you knowing that my computer is visiting your web site. I'm not okay with third parties such as Google, Facebook ("like" buttons, anyone?) or some advertiser automatically knowing that as well.
Same problem with Gmail. They look at and analyse your emails to send you those targeted ads, remember? You pay with your privacy to use it. Which may be fine. But you also pay with my privacy, each time you send me an e-mail, and each time I send one back. That is definitely not fine.
Personally, my heuristic for privacy is this: By default, don't sacrifice your privacy. Think twice before you do. And never ever sacrifice others' privacy without their explicit, informed consent.
I read someplace that 60% of the English language web sites use google analytics. add in any DNS requests passing through google's DNS, adwords js views, google searches etc and it's not hard to assume they can see pretty much whatever they need to build an advertising profile for you.
I suspect facebook is a close second with the tracking of outbound links from FB and "like" buttons all over...
At the moment we're not really seeing signs of malevolence from that corner. My worry is: what happens if those companies take a nose-dive [1] or get a new commander [2].
[1] There are plenty of examples like that floating around. Large companies that were once the kings of their tech field now seem to focus on patents as a source of income.
[2] We kinda had a sneak preview of what a change like that can do when Schmidt handed over the torch.
Conflating privacy where privacy is needed with privacy for privacy's sake is a waste of time and dilutes real privacy concerns with a bunch of "Wolf!" cries.